This invention relates to the field of metal forming tools for bending metal sheeting and for closing a metal shell at a corner between a curved or straight peripheral surface portion and a straight cross bar surface portion of a double jacketed gasket assembly.
The use of double jacketed gasket assemblies having a thin metal outer shell and a resilient core of insulating material, typically asbestos, is well-known in the prior art. These gasket assemblies may be circular, square or other shapes depending on the shape of the pressure container for which the gasket is designed. These gasket assemblies may have one or more cross bars extending across the gasket for sealing between two sealing surfaces located within the outer perimeter of the gasket.
The cross bars form a relatively sharp corner having a radius of curvature where they join the perimeter of the gasket. Bending the metal shell at this corner to close the gasket assembly causes some stretching of the metal shell at the corner which may result in tearing or crinkling of the metal, particularly if the person forming the corner is inexperienced or careless.
In the past, bending rollers have been used to bend the peripheral circular and straight portions of the gasket shell, but so far as known, it has been a practice in the past to manually close the metal shell at the corners of the cross bars and the gasket assembly with a hammer or other similar hand tool. Such an operation is generally performed by a skilled laborer who uses this technique for bending the metal shell. Even a highly skilled laborer may take as much as a minute or more to close or bend over each corner of a gasket assembly by carefully hammering the metal shell at the corner to avoid tearing the metal.